TRICOPTER SITL PX4 HELP !!

I'm trying to create a SITL simulation on Gazebo for a tricopter (BoomCopter with tilt rotor - PX4 based) using sitl_gazebo.

I'm not sure what plugins to use for the motor. In the IRIS.sdf model, they have used front_right_motor_model, back_right_motor_model and so on. Can I use the same even though I have only one back motor? how is front_right_motor_model different from back_right_motor_model ?

Is there an existing Tricopter model for SITL which I can use for reference?